Liquid hydrocarbon fuel burning apparatus



kfiz v/nfor Paul tickae rl-llllll P. SCHAEF ER LIQUID HYDROCARBON FUEL BURNING APPARATUS Filed June 9 May 9, 1944.

'A further object 'tentiom it Patented May 9, 1944 LIQUID HYDROCARBON FUEL BURNING APPARATUS Paul Schaefer, Des Plaines, 111.

Application June 9, 1941, Serial No. 397,186

11 Claims.

My invention relates generally to liquid hydrocarbon fuel burning apparatus and more particularly to improvements in apparatus of this character which is adapted for operation at low fuel consumption rates as may be required, for example, in domestic hot water heating systems.

It is a primary object of my invention to provide an improved liquid hydrocarbon fuel burning apparatus, or oil burner, which may be operated at a very low fuel consumption rate without the deposition of a carbon residue and will be effective to supply heat uniformly at ahigh temperature.

It is a further object to provide an'oil burner in which the danger ofclogging of the fuel line bycarbon deposition isavoided.

A-further object is to provide an improved oil burner which overcomes the difficulties inherent in utilizing natural draft, by utilizing a mechanical blower for supplying the air for combustion, and which will continue burning throughout short interruptions in the operation of the blower.

A further object is to provide an oil burner having a forced draft, in which combustion takes place at a sufficiently high temperature to corisume any carbon which may be deposited during intervals when the forced draft may be interrupted.

A further object is to provide an oil burner of small size which will operate satisfactorily, using oil, such as No. 3 furnace oil, and which may be operated at adjustable combustion rates.

A further object is to provide a unitary oil burner and fuel supply system with an improved support, whereby it may be adjustably positioned with-respect to the apparatus to which the heat is to be supplied. e

A further object is to provide an oil burner having filtering means which is retained at a sufficiently high temperature to cause vaporization of the oil, but which is not heated to a sufficiently high temperature to cause cracking of the .oil with theresultant disadvantageous carbon deposits.

. i A further object is to. provide an oil burner having an improved filtering medium, with improved means for insulating the filteringmedium from the heat of combustion, and with an improved combustion facilitating incandescent element; V is to provide an improved oil burner which is of very simple construction, may beseconomically manufactured,-and will operate "satisfactorily over extended periods without at- Other objects will appear from the following description, reference being had to the accompanying drawing in which:

Fig. 1 is an elevational view of the oil burner assembly with parts thereof shown in fragmentary vertical section;

Fig. 2 is an enlarged fragmentary horizontal sectional view taken on the line 2-2' of Fig. 1;

Fig. 3 is a plan view of the burner body, portions thereof being shown in fragmentary section; and i Fig. 4 is'a fragmentary sectional view taken on the-line 44 of Fig. 1. 1

In the past, considerable difliculty has been experienced in providing on oil burner apparatus suitable for use in installations requiring small quantities of heat, such as would be necessary for a small domestic hot water heating system. While some of the prior oil burners could be used for this purpose, they required a certain minimum fuel consumption rate in order to continue in satisfactory operation, and in addition 'such' oil burners usually included complicated and expensive apparatus and thus made them economically unsound for such installations where a low rate of heat supply was required.

In general, the oil burner apparatus of my invention comprises a conventional oil level control device from which the oil may be discharged at a metered rate; means for feeding the discharge from this device to a porous, refractory, ceramic filtering and vaporizing disc which is maintained at a temperature just slightly above that of the vaporization temperature of the fuel supplied; a bed of porous refractory material serving to insulate the filtering disc from the heat of combustion and providing passageways for the oil vapor; an electric motor operated to supply air under low pressure over the bed of porous, refractory material; and including a central core of porous ceramic material capable of being heated to incandescence within a space at which the combustion takes place.

The invention further contemplates partially enclosing the combustion chamber with a ceramic, lined, apertured cover capable of preventing undue dispersal of the heat of combustion, with consequent maintenance of high temperature within the combustion chamber capable of insuring complete combustion of the fuel.

More particularly the apparatus comprises a standard I!) which may be in the formof a pipe driven into or threaded in a pedestal base [2. A cross T ll of unique construction is vertically adjustable upon the standard l0, being held in adjusted position by tightening a clamping screw it. The cross T M is provided with annular grooves l receiving friction and packing rings 5! of felt, asbestos composition, or similar mat rial. The screw it, upon being tightened, is adapted to draw together the lower split flange portions E8 of the cross T M and thereby cause the lower packing ring l'i frictionally to grip the extension cord 27, is suitably secured to the extremity of the pipe 22 and is adaptedtow have,

its air discharge into the pipe 22 controlled by a manually adjustable valve 28, the stem 30 of whichisthreaded through the casing 32 .of the blower and is held in adjusted position by a lock nut 34. V l v An oil level and flow rate controlling device 35, which may be of any well-known construction, is suitably mounted upon the pipe 22.;being illustrated (Fig. 4) as having its base bracket 58 securedto-a saddle ii} by cap screws G2, the saddle 45" being .held in position on the pipe 22 by a screw 45. The level at which the oil is maintained within the device 35 is indicated by a mark 45 on the housing thereof, and th1;fiOW rate at which the oil is;-discha rged from the .device 36 may be controlled by a manually adjustable element 48.

Oil is supplied-to the device 38 through a conduitilEl, the device having a plug 55 which may be removed to obtain access to a strainer for the oil supplied through the conduit 49 The oil is discharged from the device 36 through a conduit 52 which is connected by an elbow fitting 5-1 with an oil inlet tube 55.

The combustion chamber is formed in part by an inner shell 53, which communicates with the inlettube 56, being preferably Welded or brazed thereto, and an outer shell 50 which is carried by a burner bowl, nipple 52, the latter being peened overthe horizontalbottom portion of the outer shell. The nipple 62 is threadedina universal burner T 55, which is in-turn threaded onthe end of the pipe 24 and formsa support for the lower end of the fuel inlet tube 56 as well as for the outer shell 60. The upper edge of the inner shell 58 fits around the upper edge of the outer shell 60, and into an open rolled bead G5 formed about the upper edge of the outer shell, thus holding these parts in-assembled relation. The parts are also held together by the fuel inlet tube 56, the lower end of which is threaded to receive a nut 56. A gasket 68 isprovided to seal the opening in the bottom of the universal T 5 1, through which the inlet tube 56 projects.

From the foregoing, it will appear that the relative elevations of the inner shell 58 and the outer shell-65 may be adjusted by loosening the nut 65 and unscrewing the nipple 52, and the assembly then locked in such changed position by ti htening the nut 66.

The inner shell 58 has a cylindrical bottom portion 59, in the 'lowerpart of which islocated a porous filtering and vaporizing disc 15, the lower surface of which slopes downwardly toward the center to be complemental to the similar slope of thebottom of theinnershell 58, and is provided with a depending projection 12 at center.,-

The disc i0 is made of a heat resistant, porous, refractory, ceramic material, somewhat similar to a fire brick but sufiiciently porous to be capable of absorbing an amount of oil equal to its own weight. The pores in this material are of a sponge-like character and the material is capable of raising the oil by capillary attraction. Above the porous filtering and vaporizing disc ii! is placed a layer is of fragmentary particles of a porous, ceramic material which may be of the same characteras employed for the disc :0. The fragments are of non-uniform size and shape, in

the order of A to in maximum dimension, and are uniformly distributed within the cylindrical portion 59 of the inner shell 58 as well as in the lower part of the flared portion it of the inner sheil. These fragments form a bed permitting free flow of the vaporized oil and insulating the disc to from the high temperatures of combustion, as will be more fully described hereinafter.

A central core 78 is likewise composed of a reiractory, porous, ceramic material and is secured in a metallic cup 80 which rests upon the top of the filtering and vaporizing disc 'ii'l and may be secured thereto with a suitable refractory cement. The core iii maybe provided with a central heat conducting rod 82 made of suitable metal, such as copper or brass, or for economys sake, of steel. This rod 82 is preferably riveted to the cup 88.

I Directly above the top of the layer I4 of the crushedceramic material is provided a row of air discharge ports 85, these ports, as best illustrated in Fig. 3, being directed inwardly in a non-radial direction, preferably tangential to the cylindrical core 18, as indicatedby the air flow lines of Fig.

3. These ports maybe conveniently formed by punching at an angle to the surface. It will be understood that the air discharged by the blower 2-5, as regulated by the valve 28, flows through the pipe 22 through the passageways 20 of the cross T M, and thence through pipe 24, universal T 54, and nipple 62, into the space between the inner shell 53 and the outer shell 65, and thus reaches the air discharge ports 84.

A dome-like shell 86 has its lower rim resting upon an annular shoulder 81 suitably formed near the upper edge of the inner shell 58 and has a porous refractory lining B8 suitably cemented thereto. Th shell may also be provided with dents 98 to aid in holding the lining 88 in place. The bottom edge surface of the lining 88 forms a ledge 9! directly above the points at which the air flows into thecombustion, chamber 92. An opening 93 formed in the top of the dome shell 86 may be located beneath the central heating flue 94 of a hot water boiler 96, as indicated generally in Fig. 1. e

I The installation may be such thatgthere, will be a slight amount of clearanceifor example, 4;") betweenthe upper end of; the dome shell 86 .and the lower end of the flue. 94to provide for the admission of air, although under ordinary operating conditions such additional air will not berrequired for complete combustion. It is onlyi'when the burner is operating at a high combustion'rat'e thatit'may be desirable. to admit additional air through this space. V Y

A tapped hole; normally closed by a screws-I, may be provided in the ball cross T M for attachment of an air pressure gauge forte-sting p rp ses. a

In installing the burnenthe base I2 is. positioned uponorxsecured to the floor with the standard I n as close to vertical as possible. The burner apparatus is then attached to the standard at the desired elevation, and adjustment made to secure the proper oil level with reference to the position of the porous filtering and vaporizing disc 10. This latter adjustment may conveniently be effected by screwing the nipple 62 outwardly or inwardly as required, and making the necessary adjustment of the nut 66 on the inlet tube 56 to draw the inner shell 58 downwardly to proper position in the outer shell 60. .The inner shell 58 should be at such elevation with reference to the level of the .oil maintained by the oil level control and metering device 36 that under static conditions the lower portion of thedisc 10 will be submerged. J l I a 1 w After the oil level adjustment has been made the burner assembly may subsequently be" raised or loweredon the standard without affecting such adjustment. w .7 Having connected the conduit 49 to a suitable oil reservoir and. having connected the extension cord 21= to a suitable source of current forthe blower 26, the'burner may beignited -b'y pouring an ounce or two of oil upon the fragmentary ceramic bed-14. This oil may then be ignited and the air forcedinto the combustion chamber through the inlet ports 84 will causeit to burn at a high temperature, heating the central ceramic core 18 and cup80 in which the latter rests. The heat: from such combustion will result in some vaporization of the oil in the pores of the disc 10,

the-vapor flowing-upwardly through the bed 14 oftfragmentary, porous ceramicmaterial and beingmixed with air admitted through the ports 84 to burn with a hot flame without the deposit of carbon.

During combustion under high flame conditions the core .18 becomes heated to a temperature-at which it isincandescent thus forming a means for assuring and maintaining complete combustion of thefuel. The heat of combustion is transmitted through the core 18, andmore particularly through the central rod 82 thereof and its surrounding cup 80, to the upper surface of the -filtering and vaporizing disc 10. By thus heating the disc 19, the oil which is'in the interstices and pores thereof. will become heated to itsvaporiza- .tion temperature and the vapor flow upwardly through the bed 14. The bed "of ceramic fragments servesas a means partially to insulate the disc .10 from the heat of the burninggases, only sufficient heat being transmitted through the cup 80, core-i8 and rod 82 to maintain the disc 10! at the vaporization temperature of the fuel. The cup 80 prevents liquid fuel from being drawn into the .highly heated core 18, so that-the latter remains free from carbon deposits.

.Itwill be noted thatthe lower edge of the lining 88 overhangs the ports84, forminga generally annular pocket. between it and the .uppersurface ofthe. bed 14,, which facilitates very complete combustion in this space because of the excess ofairtherein., V In order to function properly, the filtering and vaporizing disc, 1.0 should be made of a very pp rous,, capillary, ceramic. material which will act as a sponge to draw the fuel to the upper surface of the disclil. A substance known as fG Z G (G 'orG -23) porous fire brick manufactured by the P- GreenQFireIBrick 00.; of Mexico, Missouri, operates very "satisfactorily. This material'is a fire clay which is so porous 'thatits specific gravity is about one-third that of ordinary fire brick. The disc 1Q should fit the inner shell sufficiently losely to prevent particles forming the bed 14 from getting into the oil supply tube The jets of air discharged into the combustion chamber through the ports 84 are at an angle to the radii of the inner shell 58 so that they. strike the central core 18 substantially tangential to the cylindrical surface thereof. As a result, the burning vapors form a flame swirling about the central core, maintaining this core at the desired temperature at which it is incandescent.

The core 18, lining 88, and the fragmentary bed M are preferably made of the same porous, ceramic material as is used for the disc 10. The porosity of this material along the surfaces exposed to the flame and the heat thereof is an important factor in the satisfactory operation of the burner, not only because the surfaces will more rapidly be heated to incandescent temperature, but also because the minute openings formed therein serve as pockets in which complete combustion will readily take place. I

Since the fuel enters the inner shell 58 atthe bottom thereof, and the lower portion of the shell is prevented from attaining a high temperature by the incoming air supply and because of the heat insulation provided by the bed 14, there is no tendency whatsoever for carbondeposits-to form at the fuel inlet provided by the end of the fuel tube 56. The downward projection 12 formed at the center of the bottom surface of the disc 10 projects partially into the oil inlet of the inner shell 59 so that as longas oil is being supplied it will be drawn upwardly by capillary attraction into the disc 10 and the oil will not bepermitted .to stagnate at this point and be heated to a temperature at which a car'- bon deposit might form. A l 1.

Since a natural draft is not depended upon for the operation of the apparatus, uniformconditions of operations are assured. The rate at which air is supplied by the blower is adjusted by the valve 28 to be adequate to support combustion at the desired rate without furnishing a great excess. However, even if the operation of the blower should be temporarily stopped due to an interruption in the current supply to the motor thereof, the flame in the combustion chamber will not become extinguished, but combustion will continue satisfactorily for a considerable period. This is due to the fact that the combustion chamber is well insulated against the loss of heat by the bed 14 and the lining 88, and to the fact that the porous, ceramic material will remain incandescent for a considerable length of time after the supply of air is interrupted.

Under such conditions of interrupted air supply, combustion will naturally take place at a lower temperature after a short time, and as a result, under these conditions some carbon may be deposited upon the inner walls of the combustion chamber. However, upon resumption of the supply of air, combustion will again take place at such high temperature that any such carbon deposit will be burned away. 2

The burner is capable of satisfactory operation using the lower and less expensive grades of fuel, such as a refined No. 3 furnace oil, which is of particular advantage in installations in buildings heated by oil burners, using such oil as fuel because a separate oil supply will therefore not be necessary for the smaller burner. Naturally its operation is most satisfactory when a higher grade of fuel oil, such as No. 1 furnace oil, or distillate, is used. 1 I

The rate offuel supply may be readily adjusted by means of the adjustable flow regulating valve 48 and the apparatus will operate very satisfactorily at very low settings of this valve, a setting so low as .to allow the flow of one quart of oil in fourteen and one-half hours having been found to be possible. By virtue of the fact that the burner will thus operate at very low fuel consumptionrates, it is feasible to use the low fuel combustion rate when it is desired merely to maintain a pilot flame. The apparatus is thus admirably adapted for use in an automatic system in which the fuel flow rate is thermostatically controlled, since it is unnecessary to provide a gas pilot, or other igniter, and the usual complicated and expensive controlling devices therefor.

When a number of burners are operated from a common oil flow regulating device, or from a common blower, or both, their operation is facilitated by virtue of the fact that the filtering and vaporizing discs of the different units may be made tov serve as means substantially to equalize the rates of fuel flow to their respective combustion chambers. The manner in which the filtering and vaporizing discs function to accomplish fuel to vaporize too rapidly, such rapid vaporization will result in lowering the effective level of the fuel in the disc so that the area of the fuel surface which is exposed to the higher temperature is decreased and hence the rate of vaporization will be reduced. The consequent reduction in the heat of combustion will result in a lower rate of vaporization. The filtering and vaporizing discs 10 may thus form the control elements of a self-compensating system for assuring reasonably uniform distribution of the fuel among several burners connected to a common oil level and flow rate determining device, Whenever individual control of the combustion rates of the several burners is not required.

The air discharged into the combustion chamber through the ports 84 has an ejector effect in causing flow of the fuel vapor through the bed 14, particularly along the outer edge portions thereof and, as previously indicated, this results in blue flame combustion immediately adjacent the ports 84 and in'the annular space between the lower edge of the lining 88 and the upper surface of the bed 14. When the burner is operating under low flame conditions, with the fuel flow rate adjusting valve very nearly closed, combustion will take place primarily in this annular space. Under these conditions, the fact that this spaceis defined in part by the lower edge of the lining 88 and by the upper surface of the bed 14 is of importance because these ceramic surfaces become incandescent, radiating sufiicient heat to maintain complete combustion in and adjacent this space, despite the low of fuel supply. Thus, the lower edge of the lining 88 performs the functions which are otherwise performed mainly by the central core 13, namely, of maintaining an incandescently hot surface near the space in which combustion is taking place, serving. by radiation to heat theair and fuelvapor'mixture to a temperature at which rapid and complete combustion will take place.

Under low flame operating conditions the projection l2 assures the maintenance of a continuous supply of fuel, and forms a safeguard against extinguishment of the flame due to a rapid vaporization of the availablev fuel with consequent entire lack of fuel for a succeeding period, which might otherwise occur.

When operating under high flame conditions, the jets of flame formed by the air entering through the ports 84 impinge tangentially along the cylindrical surface of the core 18. The resultant heat conducted through the latter and through the cup 80, as well as the central rod 82, maintains the rate of vaporization of the fuel in and at the surface of the disc 10 sufficiently high to consume the liquid fuel at the necessary high rate. Since the core 18 is thus raised to a relatively high, temperature, it is essential that its pores be kept free from the liquid fuel and thisis one of the reasons that the lower end of the core is enclosed in the cup 80. While the use of the central core stem or rod 82 is not essential to the satisfactory operation of the apparatus, it performs the useful function of providinga hot spot at the center of the vaporizing disc 10, so that even though combustion is not taking place at a rapid rate there will be some vaporization of the fuel and combustion will thus be maintained. The metal cup 8%] likewise performs this function of assuring the transmission of sufiicient heat to the vaporizing disc "it to securevaporization at t he rate necessary to maintain the desired fuel combustion.

From the foregoing it. will appear that the operation of the apparatus comprises essentially vaporizing the fuel at a relatively low temperature and burning it in a combustion chamber at a relatively high temperature, preferably a temperature at which the porous, fire resistant, ceramic material becomes incandescent. Be- .cause the vaporization takes place at a low temperature and combustion takes place at a high temperature, carbon deposits are negligible.

While the disc 10 thus does not become clogged with carbon deposits, it may become clogged with impurities in the fuel, and when this occurs the disc may readily be replaced. Removal may be accomplished quickly and easily by loosening the clamping screw I6, swinging the apparatus from beneath the boiler 96, and removing the dome 86, 88, whereupon after having removed the ceramic fragments forming the bed 14, the disc may be raised, using thev core l8 as a handle. As previously stated, the cup 80. is preferably secured to the disc Iii by refractory cement, but this is not essential. However, a cemented connection between these parts is desirable to secure good heat conduction between the cup and disc Ill.

In Fig. 1 of the drawing the burner isshown approximately one-half normal size. From this advantages of theinvention' are present to the greatest extent only when the burner is ofrela' tively small size; 1

it will' be noted that 'combustion takes are nearly exclusively. within the dome housing 83 (except under very high flame conditions) and thus any noise produced as a result of the combustion is acoustically damped by the porous walls of the lining 88 and the bed 14 as well as the core 78.

In general the operation of the burner will be found 'to be satisfactory under maximum oil flow settings when, to some extent at least, combustion takes place at the level of the horizontal air streams directly above the'surface of the bed 14, which may be considered as a hearth.

If the combustion takes place to an appreciable extent above and outside the dome 86, 88, or if carbon is deposited within the combustion space, the rate of fuel feed should be reduced. For the minimum fuel feed rate it is sufficient if the flow adjusting valve is positioned so that a flame is maintained and so that upon an increase in the fuel flow rate, the burner will accommodate itself to such increased fuel supply and burn with a larger'flame.

While I have shown and described a particular embodiment of my invention, it will be apparent to those skilled in the art that numerous variations and modifications may be made without departing from the underlying principles of the invention. I therefore desire, by the following claims, to include within the scope of my invention all such'modifications and variations by which substantially the results of my invention may be obtained through the use pf substantially the same or similar means.

I claim:

1. In a liquid fuel burner, the combination of a fuel level and flow rate adjusting device, a power operated blower secured to said device, a fuel combustion chamber formed by an inner casing and outer casing spaced from and surrounding said inner casing, a dome partially closing said inner casing, means to conduct air under pressure from said blower to the space between said outer casing and said inner casing, said inner casing having a plurality of ports directed horizontally at an angle to the radii of the inner casing which intersect the ports respectively, means to supply liquid fuel from said device to the bottom of the inner casing, a porous refractory ceramic disc located at the bottom of said inner casing and forming a means for filtering and vaporizing the liquid fuel, a bed formed of fragments of a refractory material located above said disc and forming a means for partially insulating said disc from the heat of combustion above said bed, a refractory core located within said bed and extending above the upper surface thereof, a heat conducting cup surrounding the lower portion of said core and resting upon said disc, and a central stem within said core and forming a heat conducting path from the top portion thereof to said cup, whereby the heat of combustion will be transmitted through said core, stem and cup to said disc to insure vaporization of the liquid fuel therein.

2. In a liquid fuel burner, the combination of means defining a combustion chamber, a disc of porous refractory material located in the bottom of said means, means to supply liquid fuel to said disc, a bed of refractory fragments positioned above said disc, means to conduct heat from the space in the combustion chamber above said bed to said disc, and means to supply air under pressure to said space.

3. In a liquid fuel combustion apparatus, the combination of an outer shell and an inner shell spaced from one another to form an air flow combustion chamber.

passagewaygseiid inner shell forming the lower portion of a combustion chamber and having air passage ports leading from the space between the shells to the combustion chamber, means to supply air under pressure to the space between said shells, means to supply liquid fuel to the bottom of said inner shell at a controlled rate and to a predetermined maximum level, a porous capillary refractory element in the bottom of said'inner'shell, means to conduct heat from the combustion chamber to a portion of said element, and means to protect the remaining portion of said element from the direct heat of combustion, said last named means providing a plurality of passageways for conducting fuel vaporized within or adjacent said element to the 4. In a liquid fuel burner apparatus, the combination of a receptacle, a hearth bed located in said receptacle and formed of porous refractory fragments, a central core extending above the surface of said hearth and formed'of a porous refractory material, a dome element having an opening in the top thereof and partially covering said hearth, said dome element having a lining of porous refractory material, means to supply vaporized fuel through said bed of refractory fragments, and means to supply air for combustion in a plurality of generally horizontal jets directly above thehearth surface and in a direction to cause swirling flow about said core and inside the lining of said dome, whereby said porous refractory material of said core and lining may be heated by the combustion reaction between the air supply and the vaporized fuel to a temperature of incandescence and thereby radiate sufficient heat within said combustion space to assure complete combustion of said fuel vapor.

5. In a liquid fuel burner, the combination of a shell, an element made of porous capillary refractory material in the bottom of said shell, constant level means for supplying fuel oil to the bottom of said element, means for conducting heat to said element to cause vaporization of the fuel supplied thereto, porous means for insulating said element in part from heat in the space thereabove, said means forming a large number of passageways for the upward flow of fuel vaporjrom said element, means for supplying air for combustion to the space above said means, and an apertured dome having a lining of refractory material partially closing the top of said shell.

6. In a liquid fuel burner apparatus, the combination of a receptacle, a hearth bed located in said receptacle and formed of porous refractory fragments, a central core extending above the surface of said hearth bed and formed of a porous refractory material, a dom element having an opening in the top thereof and partially covering said hearth bed, a lining of said porous refractory material in said dome element and forming a ledge overhanging the outer edge of said hearth bed, means to supply oil vapor through said hearth bed, and means to supply air for combustion in aplurality of generally horizontal jets between said hearth surface and said overhanging ledge.

7. In a liquid fuel burner apparatus the combination of a receptacle, a hearth bed in said receptacle and comprising porous refractory fragments forming an irregular top surface, a central cylindrical core extending above the surface of said hearth and formed of a porous refractory material, a dome element having an opening in the top thereof and, partially covering said 'hearthrsaid: dome, elementhavins ,a lining of refractor materiahmejans to supply vaporized fuel through said bed. of, refractory fragments,

an s-means to supply air for combust Q in a plurality of generally horizontal jets directly above. the hearth surface, and in a direction genwally-"tangential to said core to c use swirlin now about said core and: inside the lining of said dome; whereby said porous, refractory mat'erial' of said core and. lining may be heated toincandescenoe. and thereby radiate heat within" said combustion space to facilitate complete combustion of the vaporized fuel.

8; Ina liquid fuel burner, the combination of means defining a combustion chamber, a layer of porous refractory material located in the bottom of said means, constant level means supplying liquidfuel to. said'refractory material to immerseyitv to a; predetermined level, means to of said inner shell at a controlled'rateand t a predetermined maximum le e p ro s refractory material in. the bottom of said inner'shell and extending an appreciabledistance above said maximum fuel level, and means to conduct heat from the combustion chamber to said refractory material at a suificiently slow rate to cause vaporization of the fuel without cracking.

10. In a liquid fuelburner, the combination of means defining a combustion chamber, a layer of porous refractory material located in the bottom of said means, means to supply liquid fuel tosaid layer of refractory material, a bedof refractory fragments'positioned above said layer, a core of porous refractorymaterial extending through said bed, and a metallic cup-surrounding the bottom; of said core to prevent flow of. fuel into said core; 7

11. In a liquid'fuel burner, the combination of means-forming a combustion chamber, a member of porous capillary refractory material-in the bottom of said chamber, constant level means for supplying fuel oil to said member, a core of porous refractory material positioned centrally above said member, metallic means enclosing the bottom of said core and preventing the flow of fuel from said member to said core, a bed of fragmental refractory material above said member and surrounding said metallic means, and means to supply jets of air in a horizontal direction above said bed and toward said core.

PAUL SCI-IAEFER. 

